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Search Results: 1 - 10 of 401496 matches for " M. Thiel "
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Pro-cognitive drug effects modulate functional brain network organization
Carsten Giessing,Christiane M. Thiel
Frontiers in Behavioral Neuroscience , 2012, DOI: 10.3389/fnbeh.2012.00053
Abstract: Previous studies document that cholinergic and noradrenergic drugs improve attention, memory and cognitive control in healthy subjects and patients with neuropsychiatric disorders. In humans neural mechanisms of cholinergic and noradrenergic modulation have mainly been analyzed by investigating drug-induced changes of task-related neural activity measured with functional magnetic resonance imaging (fMRI). Endogenous neural activity has often been neglected. Further, although drugs affect the coupling between neurons, only a few human studies have explicitly addressed how drugs modulate the functional connectome, i.e., the functional neural interactions within the brain. These studies have mainly focused on synchronization or correlation of brain activations. Recently, there are some drug studies using graph theory and other new mathematical approaches to model the brain as a complex network of interconnected processing nodes. Using such measures it is possible to detect not only focal, but also subtle, widely distributed drug effects on functional network topology. Most important, graph theoretical measures also quantify whether drug-induced changes in topology or network organization facilitate or hinder information processing. Several studies could show that functional brain integration is highly correlated with behavioral performance suggesting that cholinergic and noradrenergic drugs which improve measures of cognitive performance should increase functional network integration. The purpose of this paper is to show that graph theory provides a mathematical tool to develop theory-driven biomarkers of pro-cognitive drug effects, and also to discuss how these approaches can contribute to the understanding of the role of cholinergic and noradrenergic modulation in the human brain. Finally we discuss the “global workspace” theory as a theoretical framework of pro-cognitive drug effects and argue that pro-cognitive effects of cholinergic and noradrenergic drugs might be related to higher network integration.
Weak ergodicity breaking in an anomalous diffusion process of mixed origins
Felix Thiel,Igor M. Sokolov
Physics , 2013, DOI: 10.1103/PhysRevE.89.012136
Abstract: The ergodicity breaking parameter is a measure for the heterogeneity among different trajectories of one ensemble. In this report this parameter is calculated for fractional Brownian motion with a random change of time scale, often called "subordination". We proceed to show that this quantity is the same as the known CTRW case.
Scaled Brownian motion as a mean field model for continuous time random walks
Felix Thiel,Igor M. Sokolov
Physics , 2013, DOI: 10.1103/PhysRevE.89.012115
Abstract: We consider scaled Brownian motion (sBm), a random process described by a diffusion equation with explicitly time-dependent diffusion coefficient $D(t) = D_0 t^{\alpha - 1}$ (Batchelor's equation) which, for $\alpha < 1$, is often used for fitting experimental data for subdiffusion of unclear genesis. We show that this process is a close relative of subdiffusive continuous-time random walks and describes the motion of the center of mass of a cloud of independent walkers. It shares with subdiffusive CTRW its non-stationary and non-ergodic properties. The non-ergodicity of sBm does not however go hand in hand with strong difference between its different realizations: its heterogeneity ("ergodicity breaking") parameter tends to zero for long trajectories.
Analytical description of Recurrence Plots of white noise and chaotic processes
M. Thiel,M. C. Romano,J. Kurths
Physics , 2003,
Abstract: We present an analytical description of the distribution of diagonal lines in Recurrence Plots (RPs) for white noise and chaotic systems, and find that the latter one is linked to the correlation entropy. Further we identify two scaling regions in the distribution of diagonals for oscillatory chaotic systems that are hinged to two prediction horizons and to the geometry of the attractor. These scaling regions cannot be observed with the Grassberger-Procaccia algorithm. Finally, we propose methods to estimate dynamical invariants from RPs.
HIV clinic caregivers’ spiritual and religious attitudes and behaviors  [PDF]
Elizabeth A. Catlin, Jeanne H. Guillemin, Julie M. Freedman, Mary Martha Thiel
Health (Health) , 2010, DOI: 10.4236/health.2010.27120
Abstract: Based on prior research, we hypothesized that staff in an outpatient clinic caring for an HIV patient population might rely on religious and spiritual frameworks to cope with the strains of their work and that their responses to a spiritual and religious survey might reflect work-related spiritual distress. Surveys were completed by 78.7% of staff (n = 59). All respondents scored in the "moderate" range for religious and spiritual well-being as well as existential satisfaction with living. The large majority agreed that the religious and spiritual concerns of patients have a place in patient care. Nurses, (88.2% of nurse respondents) viewed assessing the spiritual needs of patients as their responsibility, (p = 0.03). While 82% of HIV clinic respondents privately prayed for patients always, often or sometimes, this did not include physicians. Physicians in this clinic setting appeared to be less spiritual and religious, based on their survey responses, than coworkers and than US physicians in general. The majority of clinic physicians (78%) believed that God does not suffer with the suffering patients, in contrast to the majority of support staff (69%) and nearly half of the nurses, who believed that God does suffer with them, (p = 0.018). Contrary to our expectation, respondents did not report work-related spiritual distress, which may be related to improved therapies that can prolong and improve patients’ lives. Survey data revealed, however, a surprising level of engagement in and reliance on spiritual and religious frameworks among nurses and support staff. Whether the absence of measured spiritual distress is linked, in a causal rather than random manner, to spiritual and religious reliance by certain of these health care providers, is unknown.
Colonic perforation with duodenal-colic fistula formation by a biliary stent in a liver transplant recipient  [PDF]
Christopher M. Moore, Raza Hamdani, Hector Ferral, David H. Van Thiel
Open Journal of Gastroenterology (OJGas) , 2012, DOI: 10.4236/ojgas.2012.22019
Abstract: Endoscopic retrograde cholangio-pancreatography (ERCP) is increasing utilized in the setting of liver transplantation for a number of post-operative related biliary issues. Although ERCP represents an excellent technology, it is not without attendant risk including sepsis, bleeding and perforation. In this case report, the first of its kind, is described the occurrence of a migrated biliary stent induced duodenal-colic fistula formation in a liver transplantation patient who had required dual biliary stenting given post-operative biliary structuring. The placement of dual stents and their size are likely implicated in the cause of perforation. The enteric anatomy and the medical immunosuppression likely contributed to a delay in diagnosis and worse outcome.
Prefrontal Neural Activity When Feedback Is Not Relevant to Adjust Performance
Jale ?zyurt, Mareike Rietze, Christiane M. Thiel
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036509
Abstract: It has been shown that the rostral cingulate zone (RCZ) in humans uses both positive and negative feedback to evaluate performance and to flexibly adjust behaviour. Less is known on how the feedback types are processed by the RCZ and other prefrontal brain areas, when feedback can only be used to evaluate performance, but cannot be used to adjust behaviour. The present fMRI study aimed at investigating feedback that can only be used to evaluate performance in a word-learning paradigm. One group of volunteers (N = 17) received informative, performance-dependent positive or negative feedback after each trial. Since new words had to be learnt in each trial, the feedback could not be used for task-specific adaptations. The other group (N = 17) always received non-informative feedback, providing neither information about performance nor about possible task-specific adaptations. Effects of the informational value of feedback were assessed between-subjects, comparing trials with positive and negative informative feedback to non-informative feedback. Effects of feedback valence were assessed by comparing neural activity to positive and negative feedback within the informative-feedback group. Our results show that several prefrontal regions, including the pre-SMA, the inferior frontal cortex and the insula were sensitive to both, the informational value and the valence aspect of the feedback with stronger activations to informative as compared to non-informative feedback and to informative negative compared to informative positive feedback. The only exception was RCZ which was sensitive to the informational value of the feedback, but not to feedback valence. The findings indicate that outcome information per se is sufficient to activate prefrontal brain regions, with the RCZ being the only prefrontal brain region which is equally sensitive to positive and negative feedback.
High-Dose Intra-Dermal Hepatitis B Vaccine in a Liver Transplant Patient Who Failed Prior Intramuscular Vaccination: A Brief Case Report  [PDF]
Sonu Dhillon, Kartik Sampath, Christopher M. Moore, Anil Dosanjh, David H. Van Thiel
World Journal of Vaccines (WJV) , 2013, DOI: 10.4236/wjv.2013.31003

Hepatitis B virus (HBV) chronic infection represents a significant cause of morbidity and mortality worldwide. While traditional intramuscular (IM) HBV vaccination is an excellent method for robust and sustained seroconversion in healthy individuals, its efficacy in chronic liver disease is sub-optimal and scant data exists in the post-liver transplant state. Importantly, HBV complications are even more severe in these same immunocompromised populations. Intra-dermal (ID) vaccination has shown initial promise as a successful alternative to achieving HBV seroconversion in patients refractory to standard vaccination protocols. Herein is a case report of a 61 year-old female who underwent liver transplantation for chronic HBV infection and achieved HBsAg seroconversion with a robust HSsAb titer with ID vaccination after having failed both standard and double dose IM vaccination.

Successful transjugular intrahepatic portal-systemic shunt in an ineligible liver transplant patient with primary biliary cirrhosis with refractory ascites and aplastic anemia  [PDF]
Christopher M. Moore, George Behrens, Hector Ferral, David H. Van Thiel
Open Journal of Gastroenterology (OJGas) , 2013, DOI: 10.4236/ojgas.2013.31001

A transjugular intrahepatic portal-systemic shunt (TIPS) is a standard way to decompress the portal system in cirrhotic patients as a bridge to orthotopic liver transplantation (OLT). Traditionally, TIPS has been indicated for certain portal hypertensive sequelae such as refractory ascites, varices treatment and even hepato-hydrothorax. Herein is a case report on the efficacy of TIPS in an OLT ineligible patient with primary biliary cirrhosis and aplastic anemia who had developed refractive ascites requiring serial paracentesis and esophageal varices. He survived 2.5 years post-TIPS placement and died from complications related to severe leucopenia and the development of sepsis.

Cross recurrence plot based synchronization of time series
N. Marwan,M. Thiel,N. R. Nowaczyk
Nonlinear Processes in Geophysics (NPG) , 2002,
Abstract: The method of recurrence plots is extended to the cross recurrence plots (CRP) which, among others, enables the study of synchronization or time differences in two time series. This is emphasized in a distorted main diagonal in the cross recurrence plot, the line of synchronization (LOS). A non-parametrical fit of this LOS can be used to rescale the time axis of the two data series (whereby one of them is compressed or stretched) so that they are synchronized. An application of this method to geophysical sediment core data illustrates its suitability for real data. The rock magnetic data of two different sediment cores from the Makarov Basin can be adjusted to each other by using this method, so that they are comparable.
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